Compressed air supply system for vehicle compressed air installation and process for controlling said system

ABSTRACT

An air compressor, from whose outlet a supply line leads to an air drier for the purpose of supplying the compressed air system. On the outlet side of the air drier, the supply line branches into a plurality of line branches that lead to at least two consumer circuits. The pressure in the consumer circuits can be monitored by pressure sensors. Furthermore, control electronics are provided which are connected to the pressure sensors. The consumer circuits can be disconnected from the compressed air supply by a closing member that is disposed in the respective supply line branch and can be switched by the programmable control electronics. By means of this, the supply of compressed air into the consumer circuits and the withdrawal of compressed air for transfer from one circuit into the others can be controlled by the control electronics. The compressed air supply device can be used in the vehicle compressed air systems of commercial vehicles.

PRIOR ART

The invention relates to a compressed air supply device for vehiclecompressed air systems. The subject of the invention is also a processfor controlling a compressed air supply device of this kind.

EP 0 523 194 B1 has disclosed a compressed air supply device of thiskind for vehicle compressed air systems. It is provided with an aircompressor that can be shut off, in order to feed compressed air via anair drier into a reservoir. A pressure sensor disposed on the reservoirmonitors the pressure of the injected air. Its pressure value isevaluated by control electronics in order to switch the air compressoron and off. In addition, the humidity of the air in the system is sensedand the control electronics control the regeneration of the air drier asa function of pressure and humidity. EP 0 523 194 B1 contains noindications about the remaining embodiment of the compressed air systemand the safeguarding of the compressed air reservoir.

National regulations and international guidelines require the presenceof a number of compressed air consumer circuits in vehicle compressedair systems in order to assist in retaining the function of the brakesystem in the event of a failure of the brake circuit. Furthermore, areciprocal safeguarding of the circuits is stipulated so that if onecircuit fails, the function of the undamaged circuit is retained.Therefore, overflow valves with limited return flow are disposed on theoutlet side of the air drier of the compressed air system, and severalof them are combined into one safety valve, for example according to DE42 09 034 A1. In addition to the object of distributing the compressedair to the various consumer circuits and safeguarding these in relationto one another in the event of a failure of a circuit as well as againstthe failure of the air compressor, here, moreover, the primarilyimportant filling of selected consumer circuits is assured. Withoverflow valves of this kind, the system-specific opening and closingpressures are determined based on structural conditions and are notsubject to any outside influences when the compressed air system of thevehicle is operated.

ADVANTAGES OF THE INVENTION

The compressed air supply device according to the invention has theadvantage over the prior art that in a vehicle specific manner or as afunction of the operating conditions of the compressed air system or thevehicle, the programmable control electronics can select and control orregulate the supply of compressed air into the consumer circuit and thewithdrawal of compressed air from a circuit for transfer into anothercircuit or for the purpose of regenerating the air drier. As a result,in comparison to the prior "rigid", i.e. defined operating mode of thecompressed air supply device, this permits the achievement of a morerapid operational readiness of the compressed air system, an energysavings in the operation of the air compressor, an increased securityfrom the loss of compressed air when a circuit is damaged, a filling ofthe consumer circuits to different, changeable pressure values, and aneconomical regeneration of the air drier that fulfills the requirements.In order to adapt the compressed air supply device to various vehiclecompressed air systems or changed operating conditions, the only thingrequired is an intervention into the control electronics by inserting orchanging a corresponding control element.

Advantageous improvements and updates of the compressed air supplydevice are possible by means of the measures setforth hereinafter.

With the equipping of the compressed air supply device, which equippingis extraordinarily simple in terms of the device, the above-mentionedadvantages are achieved, without jeopardizing the operational safetysince the suggested locking members, the pressure sensors, and thecontrol electronics have a high degree of functional safety.

However, if the proven pneumatic-mechanical safeguarding of thecompressed air system, for example according to DE 42 09 034 A1 shouldbe retained, then the embodiment of the compressed air supply devicerepresents an advantageous embodiment.

In contrast, with the measure setforth a simplification of the devicecan be achieved by virtue of the fact that the overflow valves can beswitched directly by the control electronics or, can be switchedindirectly by them.

With the improvement of the invention described herein, the availabilityof control pressure is assured on both the air compressor side and theconsumer side for switching the overflow valves as described.

With the unlikely event of a failure of the control electronics, theproven pneumatic-mechanical safeguarding of the consumer circuits can beachieved by means of the overflow valves.

With the improvement of the invention disclosed, the possibility ofelectronic control of the pressure fluid supply device is also logicallyextended to the safety valve that is used as an overflow protection aswell as being consulted for controlling the regeneration of the airdrier.

If on the other hand, the known pneumatic-mechanically controlledembodiment of the safety valve is retained as a pressure limiting valvein the compressed air supply device, then the measure setforth alsopermits it to be controlled by the control electronics.

By means of the control electronics that monitor the state of thecompressed air system, it is possible to initiate operation of the aircompressor or to switch it on or off in a simple manner that fulfillsthe requirements and is also in accordance with economical criteria.According to the improvement of the invention setforth, the controlelectronics can use data which indicate the operating state of the drivemotor of the vehicle.

The process according to the invention is for controlling a compressedair supply device for vehicle compressed air systems and, distinguishesitself advantageously in that by means of the control electronics, theavailability of compressed air on the supply side in the motor vehiclecompressed air system can be varied in such a way that the injection ofcompressed air into consumer circuits that are possibly used fordifferent purposes can be carried out in a pressure-dependent andtherefore also use-dependent manner according to logical criteria.

Advantageous improvements of the process disclosed, for example, therequirement of the regulations that pertain to permission to operate thevehicle, can be fulfilled by means setforth herein.

With the process feature disclosed, e.g. the operational readiness ofthe vehicle can be brought about in an accelerated manner.

Furthermore, it is possible to advantageously protect another consumercircuit against increased pressure load when the selected circuitrequires a higher operating pressure or has an increased compressed airconsumption, for example for the pneumatic shock absorption of thevehicle.

The switching on of the air compressor for a short time can be preventedin a simple manner with the process feature.

For example in the event of an unsealed or leaky consumer circuit,during the further operation of the compressed air system, a loss ofcompressed air as well as an increased strain on the compressed airsupply device is prevented by means of the measure indicated herein.

In a suitable manner, this kind of state of the compressed air system iscommunicated to the driver of the vehicle so that measures can be takento rectify the malfunction.

The process is a significant advantage for the economical operation ofthe vehicle because in comparison to the usual operating mode of thecompressed air supply device, other criteria can be used, for example,whether the drive motor of the vehicle is operated at a high outputlevel and therefore a switching on of the air compressor is not advised.

The measures set forth are used in a suitable manner to exploit kineticenergy intrinsic to the vehicle for the operation of the air compressor.

The process features described herein can be used for the operation ofthe air compressor, by virtue of the fact that when not needed, eitherthe compressed air supplied is diverted to a relief point or the aircompressor is uncoupled as needed from the drive or the air supply ofthe driven air compressor is switched off by the control electronics.

From the standpoint of compressed air consumption balance, the processis advantageous because by means of it, the different demand forcompressed air occurring in the consumer circuits can be compensated forby the control electronics.

With the process feature set forth, particularly dry compressed air isadvantageously used for regenerating the air drier so that the requiredregeneration air volume can be kept relatively low.

In lieu of the above-described measures, the regeneration of the airdrier can be carried out in a known manner by the withdrawal ofregeneration air from a separate container.

Through corresponding programming of the control electronics, differentoperating modes are possible for the regeneration control.

Finally, through the use of the process steps indicated, it isadvantageously possible to supply the air drier with complete dryingcapacity for the subsequent initial operation of the vehicle and toprevent the freezing of the valve by means of blowing out accumulatedwater in the region of the safety valve with the regeneration airdiverted to the relief point. It is therefore possible to dispense withan electrical heating of the safety valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are shown in simplified form inthe drawings and are explained in detail in the following description.

FIG. 1 is a switching diagram of a compressed air supply device with acontrollable overflow valve in the consumer circuits,

FIG. 2 is a switching diagram according to FIG. 1, with a seriesconnected overflow valve as well as a switchable closing member in theconsumer circuits, and

FIG. 3 is a switching diagram of a compressed air supply device withonly one switchable closing member in the consumer circuits.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The compressed air supply device 10.1, which is for vehicle compressedair systems and is schematically represented in FIG. 1 of the drawings,is preferably designated for use in commercial vehicles. The device 10.1has an air compressor 11, which is coupled to the drive motor 13 of thevehicle by means of a loose coupling 12. The coupling 12 can be switchedin an electrically controlled manner; a corresponding actuation means 14is therefore depicted.

An air supply line 17 leads from the air compressor 11 to an air drier18 that can be regenerated. A humidity sensor 19 for measuring themoisture contained in the granulate of the air drier can be connected tothe air drier 18, which moisture is removed from the compressed airsupplied by the air compressor 11. The air drier 18 can also beconnected to a container 20 for storing regeneration air, which issupplied to the air drier when removing the moisture from the granulatethat can be regenerated using the reverse flow process. In addition, ahumidity sensor 21 can be connected to the supply line 17 between theair compressor 11 and the air drier 18 and can monitor the water contentof both the compressed air supplied by the air compressor 11 and theregeneration air diverted from the air drier 18.

Between the air compressor 11 and the air drier 18, a branch line 25leads from the supply line 17 to a pressure relief point 24. A safetyvalve 26 in the structural form of a pressure limiting valve is disposedin this line and, actuated via a control line 27, limits the maximalsystem pressure in the vehicle compressed air system. Furthermore, thesafety valve 26 can be pneumatically switched into the open position viaan additional actuation means 28. An electrical heating device 29 isprovided to protect the safety valve 26 from freezing.

The supply line 17 is extended after the air drier 18 in five linebranches 17.1 to 17.5. On the outlet side of the air drier 18, aspring-loaded check valve 32 is disposed in the supply line 17, whichcloses the supply line in the direction of the air drier 18. The checkvalve 32 is bypassed by a bypass line 33 with a throttle location 34,which permits a throttled return flow of air to the air drier 18 forregeneration purposes.

The supply line branches 17.1 to 17.5 are connected to compressed airconsumer circuits I to V of the vehicle compressed air system (of theconsumer circuits I to V, only a compressed air reservoir 37.1 to 37.5is depicted). The consumer circuits I and II are service brake circuitsand like the consumer circuit III, which constitutes an auxiliary brakecircuit, are part of the brake system of the vehicle. The circuit IV isa secondary consumer circuit and the consumer circuit V is an air shockabsorber circuit.

In each of the supply line branches 17.1 to 17.5, an overflow valve 40.1to 40.5 with limited return flow is disposed upstream of the reservoirs37.1 to 37.5 of the compressed air consumer circuits I to V, viewed interms of the feed direction. These overflow valves 40.1 to 40.5 are usedfor compressed air supply and for pressure safeguarding of the connectedcompressed air consumer circuits I to V, wherein compressed air supplyis understood to mean the delivery of compressed air to the consumercircuits, which has been supplied by the air compressor 11 and dried inthe air drier 18. Diverging from the overflow valve 40.4 disposed infeed line branch 17.4, the overflow valves 40.1 to 40.3 and 40.5 areembodied as switchable closing members which can be switched by anadditional actuation means 41 into a position that closes the associatedline branch. In the exemplary embodiment represented in FIG. 1, this isa pneumatic actuation means 41, which in the embodiment of the overflowvalve disclosed by DE 42 09 034 A1, can be a control chamber that can beacted upon by control air, in which a compression spring is disposed,which loads a sleeve piston in the closing direction. In a modificationof the exemplary embodiment, the actuation means 41 can also be anelectromagnetic or electromechanical one. The overflow valves 40.1 to40.3 and 40.5 embodied as closing members can be united in thestructural form of the four-circuit protection valve 42.1, as indicatedwith a dot-and-dash outline.

The pneumatic actuation means 41 can be respectively switched by meansof a pilot valve 44.1 to 44.4, which is embodied as a 3/2-way valve. Inaddition, a fifth pilot valve 44.5 of the same structural form isprovided in order to be able to switch the safety valve 26 via itsactuation means 28. In a spring-actuated fashion, the pilot valves 44.1to 44.5 assume a position in which a control line branch 45.1 to 45.5that leads to the respective actuation means 41 or 28 is ventilated tothe atmosphere. In its second, electromagnetically actuated position,however, the control line branches 45.1 to 45.5 are switched into theopen position. For the supply of control pressure, the control linebranches 45.1 to 45.5 are connected via a control line 46 to the supplyline 17 on the downstream side of the air drier 18, and are alsoconnected via a control line 47 between the overflow valve 40.1 and thereservoir 37.1 to the supply line branch 17.1 of the compressed airconsumer circuit I. The two control lines 46 and 47 are safeguarded inrelation to each other by means of check valves 48 and 49, which can becombined into one reversing valve 50. According to the operating mode ofthe compressed air supply device 10.1, it can also be sufficient toprovide only the control line 46 or the control line 47. The checkvalves 48 and 49 can then be dispensed with.

An additional humidity sensor 53 is associated with the compressed airsupply device 10.1 and is connected between the overflow valve 40.1 andthe reservoir 37.1 to the supply line branch 17.1 of the compressed airconsumer circuit I. In addition, pressure sensors 54.1 to 54.3 and 54.5are connected to the corresponding supply line branch 17.1 to 17.3 and17.5 between the corresponding overflow valve 40.1 to 40.3 and 40.5 andthe associated reservoir 37.1 to 37.3 and 37.5, which sensors areprovided for monitoring the pressure in the compressed air consumercircuits I to III and V.

A further component of the compressed air supply device 10.1 areelectronics 57 which carry out control and regulation functionsaccording to their programming and are described below as controlelectronics. The control electronics 57 are connected to the actuationmeans 14 of the loose coupling 12, the humidity sensors 19, 21, and 53,the pilot valves 44.1 to 44.5, and the pressure sensors 54.1 to 54.3 and54.5. Power is supplied to the control electronics 57 via lines 58. Thecontrol electronics 57 are connected to the engine control of thevehicle via a data bus 59; in addition, a line 60 leads to a statusindicator of the compressed air supply device 10.1 in the drivingcompartment of the vehicle.

All of the elements of the compressed air supply device 10.1 disposedbetween the air compressor 11 and the compressed air reservoirs 37.1 to37.5 can be combined into a device unit 63, as is indicated in FIG. 1with a dot-and-dash outline.

The compressed air supply device 10.1 has the following functions:

The valves of the compressed air supply device 10.1 assume the positionsrepresented in FIG. 1 and the air compressor 11 that is coupled to itsdrive motor 13 delivers compressed air into the supply line 17. Thehumidity is removed from the air when it flows through the air drier 18and after overcoming the check valve 32, travels into the supply linebranches 17.1 to 17.3 and 17.5. At the same time, compressed air flowsthrough the control line 46 to the pressure control valves 44.1 to 44.5.When the opening pressure of the overflow valves 40.1 to 40.3 and 40.5is exceeded, compressed air flows into the reservoirs 37.1 to 37.3 and37.5 of the compressed air consumer circuits I to III and V and afterthe opening of the overflow valve 40.4, furthermore flows through thesupply line branch 17.4 to the compressed air reservoir 37.4 of thesecondary consumer circuit IV. The opening pressures of the overflowvalves 40.1 to 40.3 and 40.5 can be adjusted by means of mechanicaladjustment in such a way that the two circuits I and II are filledbefore the other circuits III to V. With the initial operation of thevehicle, the pressure is continuously monitored in the consumer circuitsI to III and V by the control electronics 57 with the pressure sensors54.1 to 54.3 and 54.5. According to the programming of the controlelectronics 57, the filling of the compressed air consumer circuits I toV can be varied in a pressure-dependent manner. For example in the eventof an equivalent adjustment of the opening pressure of the overflowvalves 40.1 to 40.3 and 40.5, a high-priority filling of the consumercircuits I and II can be achieved by virtue of the fact that byswitching the pilot valves 44.3 and 44.4 into their magneticallyactuated position, control air is switched into the pneumatic actuationmeans 41 of the overflow valves 40.3 and 40.5 so that these assume theirclosed position. The two overflow valves 40.3 and 40.5 now function as aclosing member, which disconnects the consumer circuits III and IV or Vfrom the supply of compressed air. When the operating pressure isachieved in the consumer circuits I and II, the control electronics 57cancel the stopping of the other circuits by switching the pilot valves44.3 and 44.4 into their spring-actuated position. The consumer circuitsIII to V are now filled with compressed air.

To fill the air shock absorber circuit V to a higher operating pressurein comparison to the other circuits I to IV, the control electronics 57switch the overflow valves 40.1 to 40.3 into their position that stopsthe supply of compressed air. The compressed air supplied by the aircompressor 11 is therefore now only supplied to the compressed airconsumer circuit V. When the operating pressure of circuit V is reached,which is monitored by the pressure sensor 54.5 and is disposed below theswitch-off pressure of the safety valve 26, then if the other circuitsare full, the supply of the air compressor 11 can be switched off. Inorder to retain the increased pressure level in the air shock absorbercircuit V, the overflow valve 40.5 is switched into the closed positionthrough the injection of control pressure into its actuation member 41.If all of the overflow valves 40.1 to 40.3 and 40.5 assume their closedposition, then when the air supply is switched off, control air can betaken from circuit I using the control line 47.

Compressed air is consumed to different degrees by means of theconsumers connected to the circuits I to V. When the closed position ofthe overflow valves 40.1 to 40.3 is cancelled by the control electronics57, a pressure compensation between the circuits I to IV can take place,provided that the closing pressure of the respective overflow valve isnot exceeded. By maintaining the closed position of the correspondingoverflow valve, the control electronics 57 can also exclude circuitsother than the air shock absorber circuit V from the exchange ofcompressed air. If the control electronics 57 recognize that the limitpressure achieved when the compressed air consumer circuit is filled uphas fallen by a programmed pressure difference due to the consumption ofcompressed air, then the compressed air supply of this circuit isadmitted. For example, when the vehicle is coming down a mountain, ifthe two service brake circuits I and II are subject to an increasedconsumption of compressed air due to longer lasting braking procedures,then the remaining circuits III to V are disconnected from thecompressed air supply and preferably the two service brake circuits Iand II are filled by means of air supply. When their limit pressure isreached, the circuits I and II are disconnected and if need be, othercircuits are filled.

It can therefore be seen that the compressed air supply of thecompressed air consumer circuits I to V by means of correspondingprogramming of the control electronics 57 with regard to the initialfilling, the filling succession of the circuits, the adjustment ofdifferent operating pressures, the compensation for varying compressedair consumption in the circuits, as well as the refilling of thecircuits can be varied within wide limits. Criteria for the programmingcan, for example, be the type of vehicle, the equipping of the vehicle,and its mode of operation.

The operation of the air compressor 11 can be controlled throughcorrespondingly programming the control electronics 57. In this manner,the control electronics 57 can switch on the air compressor 11 when thevehicle is coasting in order to use the kinetic energy of the vehicle tofill the compressed air consumer circuits I to V. This can be used tofill a circuit to a pressure level that is higher in comparison to theoperating pressure in order to subsequently fill other circuits thathave a lower desired pressure with compressed air from this circuit asneeded. However, if the full output of the drive motor 13 is necessaryto propel the vehicle, by triggering the electromagnetic actuating means14, the control electronics 57 switch the air compressor 11 off byseparating the loose coupling 12. However, if the pressure dropsimpermissibly low in the service brake circuits I and II in this drivingstate, then the air compressor 11 is switched on again by the controlelectronics 57.

If the vehicle has no loose coupling 12 between the drive motor 13 andthe air compressor 11, then the compressor can be switched into neutralby virtue of the fact that by switching the pilot valve 44.5, thecontrol electronics 57 injects control air into the actuating means 28of the safety valve 26 and switches this valve into its open position.The air supplied by the air compressor 11 is now diverted to thepressure relief point 24 by means of the safety valve 26. However, it ismore economical if the air compressor 11 has a device, not shown, withwhich the suction valve is switched into an inactive state or a bypassconnection can be connected between the intake chamber and thecompression chamber of the air compressor 11.

For the control of the air compressor 11, the control electronics 57receives corresponding data from the engine control via the data bus 59.In addition, the control electronics 57 are capable of sendinginformation to a status indicator of the compressed air system disposedin the driving compartment of the vehicle in order to inform the driverwhat pressure conditions are present in the compressed air consumercircuits I to V and if need be, whether there are malfunctions. If thecontrol electronics 57 detect a defect, e.g. due to a leak, when thepressure in a consumer circuit falls below or does not achieve apredetermined pressure threshold, then the affected consumer circuit isdisconnected from the compressed air supply by switching thecorresponding overflow valve into the closed position.

To initiate and control the regeneration of the air drier 18, thecontrol electronics 57 evaluates the signals of the humidity sensors 19,21, 53. However, the control electronics 57 can receive data regardingthe temperature of the compressed air supplied, the speed of the aircompressor 11, etc. The control electronics 57, in accordance with theirprogramming and the sensor equipment of the compressed air supply device10.1, are equipped to control the regeneration duration of the air drier18 as a function of air quantity, pressure, time, or humidity. If as aresult of the measurement values of the humidity sensor 53, the controlelectronics 57 recognize that the compressed air supplied to theconsumer circuit I has an impermissibly high moisture content, then whenthere is ineffective air supply of the air compressor 11, theregeneration of the air drier 18 is initiated by the switching over ofthe safety valve 26. To this end, compressed air can be taken from theconsumer circuits I to V, which travels through the bypass line 33 viathe throttle location 34 and flows through the granulate in the airdrier 18 in the direction counter to the air supply direction. Theregeneration air absorbs moisture stored in the granulate and carries itaway to the pressure relief point 24 via the safety valve 26. By meansof corresponding switching of the overflow valves 40.1 to 40.3 and 40.5,it can be assured that the regeneration air is withdrawn from theconsumer circuit that has the highest pressure level. Or theregeneration air is taken from the consumer circuit that was filledfirst after the preceding regeneration of the air drier 18 so that itcontains particularly dry air. In lieu of this, the regeneration of theair drier 18 can also occur by means of the withdrawal of regenerationair stored in the reservoir 20. The control electronics 57 can controlthe duration of the regeneration for example as a function of time, oras a function of the pressure drop of the consumer circuit that suppliesthe regeneration air, or by sensing the moisture content of theregeneration air leaving the air drier 18 by means of the humiditysensor 21. When using the humidity sensor 19 disposed in the dryinggranulate, the beginning and end of the regeneration are controlled inconjunction with the moisture content of the drying granulate.

In addition to during driving operation, a regeneration of the air drierby the control electronics 57 can also be controlled after the vehicleis switched off, by virtue of the fact that the safety valve 26 isswitched into its open position and in the event of the withdrawal ofthe regeneration air, for example from the air shock absorber circuit V,the overflow valves 40.1 to 40.3 of the remaining consumer circuits I toIV are switched into the closed position. Since water accumulations inthe region of the safety valve 26 due to the pressure decrease duringregeneration are blown out, the electrical heating 29 that prevents thefreezing of the safety valve can possibly be eliminated. After theregeneration is over, by means of switching the pilot valves 44.1 to44.3 and 44.5 into their spring-actuated position, the controlelectronics 57 switch the overflow valves 40.1 to 40.3 and the safetyvalve 26 into their initial position shown in the drawing. When thevehicle is started up again, the air drier 18 is available with fulldrying capacity.

The second exemplary embodiment of a compressed air supply device 10.2represented in FIG. 2 differs from the first exemplary embodimentessentially in that the four-circuit protection valve 42.2 containsoverflow valves 65.1 to 65.3 and 65.5 without additional actuationmeans. In lieu of this, a closing member in the form of a stop valveembodied as a 2/2-way valve 66.1 to 66.3 and 66.5 is disposed in each ofthe feed line branches 17.1 to 17.3 and 17.5, downstream of the overflowvalves in the flow direction. When not triggered, the directional valveassumes its spring-actuated open position. In the same manner as in thefirst exemplary embodiment, the control electronics 57 can switch thisvalve into its closed position by means of the pilot valves 44.1 to 44.4through pneumatic actuation. The closing member can also be disposed inthe feed direction upstream of the overflow valves 65.1 to 65.3 and 65.5in the supply line branches 17.1 to 17.3 and 17.5. The mode of operationof the compressed air supply device 10.2, which is likewise equippedwith pressure sensors 54.1 to 54.3 and 54.5 is the same as in theexemplary embodiment according to FIG. 1.

The third exemplary embodiment of the compressed air supply device 10.3according to FIG. 3, however, is shown in a manner that is considerablysimplified in comparison to the two preceding exemplary embodiments withregard to the valves and controls. Here, a 2/2-way valve 69.1 to 69.3and 69.5 with a spring-actuated closed position is respectively disposedas a switchable closing member in each of the supply line branches 17.1to 17.3 and 17.5. The directional valves can be switched into their openposition directly by the control electronics 57 through electromagneticactuation. This compressed air supply device 10.3, too, can becontrolled in a manner that corresponds to that in the first exemplaryembodiment because of the pressure sensing in the consumer circuits I toIII and V by means of the pressure sensors 54.1 to 54.3 and 54.5 throughthe corresponding control of the directional valves 69.1 to 69.3 and69.5. In addition, the safety valve of the compressed air supply deviceis embodied in the form of a 2/2-way valve 70, which the controlelectronics 57 can electromagnetically or electromechanically switchfrom its spring-actuated closed position into the open position for thepurpose of regeneration control. In order to limit the maximumpermissible pressure in the vehicle compressed air system for safetyreasons, the directional valve 70 can also be pneumatically switchedinto its open position via a control line 71.

The foregoing relates to preferred exemplary embodiments of theinvention; it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention; thelatter being defined by the appended claims.

What is claimed is:
 1. A compressed air supply device (10.1) for vehiclecompressed air systems which comprises, an air compressor (11) providedwith an outlet, from said outlet a supply line (17) leads to an airdrier (18), said air drier includes an inlet and an outlet side forsupplying compressed air to a compressed air system,a safety valve (26)is connected to the supply line (17) to divert air to a pressure reliefpoint (24) upstream of said air dryer and down stream of the aircompressor, on the outlet side of the air drier (18) at least twocompressed air consumer circuits, whose pressure is monitored by atleast two pressure sensors, are connected to the supply line (17),control electronics (57) are provided, which are connected to thepressure sensors and at least one solenoid valve for controlling aregeneration of the air drier (18), and which control the compressed airsupply of the air compressor (11), on the outlet side of the air drier(18), the supply line (17) branches into line branches that lead to atleast two consumer circuits, a closing member disconnects the consumercircuits from the compressed air supply, the closing member beingdisposed in the respective line branch and switched by the programmablecontrol electronics (57), the closing member is an overflow valve thatis disposed in the line branch and is switched into the closed positionwith a pneumatic actuation means (41), and a 3/2-way pilot valve (44.1)is disposed in a control line of the pneumatic actuation means (41). 2.A compressed air supply device according to claim 1, in that the closingmember is a stop valve disposed in the line branch.
 3. A compressed airsupply device according to claim 2, in that the closing member is anactuatable 2/2-way valve with a spring-actuated closed position.
 4. Acompressed air supply device according to claim 2, in that the closingmember is a 2/2-way valve with a spring-actuated open position disposedat an overflow valve in the branch.
 5. A compressed air supply deviceaccording to claim 1, in that the control lines (46, 47) are connectedto both the supply line (17) and to the consumer circuit, wherein acheck valve (48, 49) is disposed in each control line (46, 47).
 6. Acompressed air supply device according to claim 5, in that a line branch(45.5) leads from the control line (46, 47) to a pressure limit safetyvalve (26), which is equipped with the pneumatic actuation means (28)and is switched into the open position by an electromagneticallyactuatable 3/2-way pilot valve disposed in the line branch (45.5).
 7. Acompressed air supply device according to claim 1, in that the pilotvalve (44.1) is electromagnetically switched by the control electronics(57) into a position in which the control line is switched into an openposition.
 8. A compressed air supply device according to claim 1, inthat a 2/2-way safety valve (70) assumes a closed position in aspring-actuated manner and is switched into an open position in anactuated fashion by the control electronics (57), or switched into theopen position by the pressure in the supply line (10.3).
 9. A compressedair supply device according to claim 1, in that the control electronics(57) are connected to an actuation means (14) for a coupling (12) fordisconnecting the air compressor (11) for a drive motor (13).
 10. Acompressed air supply device according to claim 1, in that the controlelectronics (57) are connected to an actuation means for controlling theair compressor (11) in an idle position.
 11. A compressed air supplydevice according to claim 1, in that the control electronics (57) areconnected to the engine control of the vehicle via a data bus (59). 12.A compressed air supply device according to claim 1, in that the closingmember is an overflow valve that is disposed in the line branch and canbe switched into the closed position with an electromagnetic actuationmeans.
 13. A process for controlling a compressed air supply device(10.1) for vehicle compressed air systems which comprises controlling acontrol electronics (57) for controlling the compressed air supply ofthe compressed air supply system as a function of pressure in at leasttwo compressed air consumer circuits,monitoring the pressure by thecontrol electronics (57) in at least two consumer circuits, operatingthe control electronics (57) to disconnect the consumer circuits fromthe compressed air supply as a function of a pre-programmed limitpressure that depends on the circuit, operating the control electronics(57) to connect at least two respective consumer circuits to thecompressed air supply when the pressure falls below a limit pressure bya pre-programmed pressure difference, which comprises operating thecontrol electronics (57) to select a consumer circuit for filling saidconsumer circuit with compressed air while at least one other consumercircuit is disconnected from the filling, and operating the controlelectronics (57) to connect the consumer circuit to the compressed airsupply of the air supply system in a pre-programmed order.
 14. A processaccording to claim 13, which comprises operating the control electronicsto a select a consumer circuit which is filled to a higher pressure thanthe at least one other consumer circuit (I).
 15. A process according toclaim 14, which comprises filling the at least one other consumercircuit from the consumer circuit that has a higher pressure.
 16. Aprocess according to claim 13, which comprises operating the controlelectronics (57) to disconnect the affected consumer circuit from thecompressed air supply when the pressure falls below a predeterminedpressure threshold.
 17. A process according to claim 16, which comprisescontrolling a status indicator, which is disposed in a drivingcompartment of the vehicle and is part of the compressed air system byoperating the control electronics (57).
 18. A process according to claim13, which comprises operating the control electronics (57) to switch thesafety valve (26) of the compressed air system into the position thatdisconnects the compressed air and switching the closing members of theconsumer circuits into the closed position.
 19. A process according toclaim 13, which comprises connecting the air compressor (11) to a drivemotor (13) by means of a coupling (12) that is switched by operating thecontrol electronics (57).
 20. A process according to claim 13, whichcomprises switching the air compressor (11) into a no-load operation byoperating the control electronics (57).
 21. A process according to claim13, which comprises taking the air required for the regeneration of theair drier (18) disposed in the compressed air supply device (10.1) fromthe consumer circuit which is at the highest pressure level, while theclosing member (40.1) associated with the at least one other consumercircuit is held in the closed position.
 22. A process according to claim21, which comprises controlling the regeneration duration by the controlelectronics (57) as a function of air quantity, pressure, time, ormoisture.
 23. A process according to claim 21, which comprisescontrolling the regeneration of the air drier (18) by operating thecontrol electronics (57) after the vehicle is switched off, bypresenting the safety valve (26), switching the safety valve into itsopen position and in the event that regeneration air is taken from aconsumer circuit, switching the closing member of the at least one otherconsumer circuit into the closed position, and at the end of theregeneration, switching the safety valve (26) and the closing member.24. A process according to claim 13, which comprises taking aregeneration air for an air drier (18) from the consumer circuit thatwas filled with compressed air first after the preceding regeneration.25. A process according to claim 13, which comprises taking theregeneration air from a regeneration air reservoir (20) connected to theair drier (18).
 26. A process for controlling a compressed air supplydevice (10.1) for vehicle compressed air systems which comprisescontrolling a control electronics (57) for controlling the compressedair supply of the compressed air supply system as a function of pressurein at least two compressed air consumer circuits,monitoring the pressureby the control electronics (57) in at least two consumer circuits,operating the control electronics (57) to disconnect the consumercircuits from the compressed air supply as a function of apre-programmed limit pressure that depends on the circuit, operating thecontrol electronics (57) to connect at least two respective consumercircuits to the compressed air supply when the pressure falls below alimit pressure by a pre-programmed pressure difference, and operatingthe control electronics (57) to control the filling of the consumercircuits as a function of the pressure in the circuits as well as anoutput level of a drive motor of the vehicle.
 27. A process according toclaim 26, which comprises filling the consumer circuits when a drivemotor (13) of the vehicle is driven by a weight of the vehicle during adownward run.